Patience is a virtue

The reason people recommend you separate birds is because your bird will likely bond with its birdie-friend rather than you. If the bird has bonded with the birdie-friend, it likely won't give a hoot about you unless you tamed the bird beforehand. So if you separate the birds, you have to be the single bird's best friend. You have to groom them, provide companionship, play with them, etc. It's a big responsibility. If you can't provide that kind of companionship and training, then I would just recommend keeping them together. They won't bond as well to you, but that's a small price to pay.

As for training, don't feed your birds in the morning. Instead, take a spoonful of their seed diet and place it in the palm of your hand. Place your hand in the cage next to a perch. Sit there and don't move and don't look them in the eyes. After a few minutes, the birds will climb onto your hands to eat the seed. Don't move and don't look at them threateningly. It'll also be good to practice birdie calming signals like: yawning, looking sideways, slow blinking, etc.

Also, I highly recommend Guide to a Well-Behaved Parrot by Mattie Sue Athan. Good luck